The prior art is known by the French patent application FR14/61241 describing a mechatronic unit for driving a member intended to be connected on the one hand to a DC power source and on the other hand to an ECU control unit comprising a computer for calculating a servo algorithm delivering steering and torque information, this unit comprising an actuator formed by an N-phase (where N>1) multiphase brushless electric motor, binary sensors for detecting the position of the rotor of said motor, an electronic circuit comprising a power bridge for supplying the N phases of the motor. This prior art unit further comprises an on-board electronic driver circuit free of microcontroller, computer and memory, the input of which receives this steering and torque information from the ECU and whose output controls said power bridge providing for the self-switching of the motor by combining the information from the steering and torque signal, binary probes for detecting the position of the rotor and a switching logic modulating directly the current of the continuous power source applied to each of said engine phases and in that the torque and steering information provided by the ECU is distinct from the power signal delivered only by the power source.
In the prior art, the international patent application WO2016079315A 1 also describes a mechatronic unit for driving a member intended to be connected on the one hand to a DC power source and on the other hand to an ECU control unit comprising a computer for performing a servo algorithm delivering steering and torque information, said unit comprising an actuator formed by a N-phase multi-phased brushless electric motor, binary sensors for detecting the position of said motor rotor, an electronic circuit comprising a power bridge for supplying the N phases of the motor, characterized in that it further comprises an on-board electronic driver circuit whose input receives said steering and torque information from the ECU and whose output controls this power bridge directly modulating the current of the DC power source applied to each of said motor phases and in that the torque and steering information provided by the ECU is distinct from the output power signal delivered only by the power source. The torque information is information which makes it possible to adjust, at the output of the power bridge, the position or speed of the rotor of the loaded motor.
The patent application WO2014091152 from the prior art describes an actuator driven by a brushless DC motor, while keeping the existing elements identical to the system based on a DC motor with brushes. The actuator is connected to the control system through a connector gathering the analog and/or digital signals from the position sensor, as well as the signals combining the direction and the torque to be produced by the BLDC motor. A basic electronic circuit resistant to high temperatures (>125° C.) manages the self-switching of the N phases of the motor using N probes giving the position of the motor rotor. The objective of the solution described below is to provide a technological compromise making it possible to remedy the issues mentioned above and to offer a cost-effective solution requiring no microprocessor, enabling the use of a brushless DC motor instead of a DC motor with brushes, while keeping the possibility of using a reversible polyphase motor and controlling it in both directions of rotation. The invention is thus applicable to any N-phase polyphase motor. Other examples of such mechatronic assemblies are also described in patent applications WO95/08214 and GB2013011.
The problem with the prior art is that the maximum set point speed that can be sent by the control circuit without a computer is limited by the frequency of the direction and torque information (or speed information since a given supply voltage will fix, for a given load, the torque and speed) transmitted by the controller. This direction and torque/speed information is physically a pulse width modulated control signal called PWMIN. The ECUs (Electronic Control Units) integrated in the vehicles have been designed to control electro-hydraulic valves requiring a low frequency of the control signal modulated in pulse width, in the range of 100 to a few hundred Hertz (PWMIN<500 Hz). To obtain a sufficient rotational speed of the BLDC motor for the application, an obvious solution is to increase the frequency of the pulse-width modulated control signal, which implies a significant hardware modification of the controller.
In addition, the direction and speed information returned by the mechatronic assembly to the controller allowing the application to be controlled is transmitted via separate channels, which may lead to interpretation errors by the controller resulting from the lack of synchronism between the two signals, this risk evolving in proportion to the rotational speed of the associated BLDC motor and its electronic power bridge control module. This second problem is potentially related to the problem of the maximum speed limit, but also exists independently from this problem.
A third problem concerns the extreme values of the duty cycle of the pulse-width modulated control signal (close to the values of 0 or 100%) that cannot be generated by existing controllers. An PWM control requires the use of duty cycle ranges close to extreme values in order to detect electrical faults on the PWM control line. For example, faults associated with a line break, a permanent or intermittent short circuit of the line to ground or supply voltage are found. Therefore, these duty cycle ranges cannot be used for encoding direction and torque/speed information.
This results in the loss of part of the electrical power (typically 8%) that can be transmitted to the BLDC motor, the latter being the image of the PWM control signal. This third problem is potentially related to the problem of the maximum speed limit, but also exists independently from this problem.